Hard disk drives used for long term magnetic storage of digital information are ubiquitous and essential devices in our modern world. A hard disk drive device includes one or more rotating disks within an enclosure. To use the hard disk drive to store and retrieve digital information, the hard disk drive device also includes components adapted to read and write information from and onto the magnetic disk. A “head gimbal assembly” includes a suspension, a gimbal, a flex circuit, and a slider. The slider includes one or more magnetic read-write heads that include a miniaturized transducer for reading or writing data from or onto the rotating disk, and an air bearing surface to properly position the read-write heads above the disk as the disk rotates. The disk is coated with media that can be selectively magnetized by a read-write head, to store digital information in a manner that allows for retrieval of the information, also by a read-write head.
The head gimbal assembly is attached to an actuator arm that is part of the disk drive, and is held by the actuator arm to place the slider at a location that is adjacent to but not touching the surface of the disk. As the disk spins, air flow at the spinning disk surface interacts with the air bearing surface of the slider to create a cushion or “bearing” of air located in the space between the slider and the disk surface. This cushion of air, or “air bearing,” suspends the read-write head at a desired distance from the disk surface. If the read-write head is too far away from the surface, signal loss will occur, and if the head is too close to the surface the head could contact the surface, i.e., “crash,” resulting in damage to the head or the disk and often a complete hard drive failure.
The hard disk drive industry is constantly in pursuit of new ways to increase the amount of data that can be stored on an area of a magnetic disk, sometimes referred to as “areal density.” To increase areal density, the size of an amount of stored information on a disk surface may be reduced. One way to reduce the size of an amount of data relative to a disk surface is to use a slider and read-write heads that are smaller in size compared with previous versions. Reducing the size of a read-write head may also involve reducing the size of other features of the slider, such as the sizes of attendant components of the slider, for example electrical contacts (a.k.a., “contact pads”) used to electrically connect the slider to a head gimbal assembly. Accordingly, recent developments in magnetic recording technology have involved the development of sliders having ever-smaller components, including smaller and smaller contact pads with which a slider and its integral read-write heads are electrically connected to a head gimbal assembly.
By certain approaches of increasing areal density, a slider and hard disk media may be designed to perform magnetic recording by an improved recording technique that allows for recording data as smaller-sized bits. One such technique, referred to as perpendicular magnetic recording (PMR), allows for writing individual pieces (bits) of data onto a hard magnetic disk surface in a perpendicular direction, as compared to a longitudinal direction. As another, more recent approach, smaller-sized data recordings can be placed more closely together by use of a recording medium that has a higher coercivity. To record a bit of data onto the higher coercivity medium, the medium is heated at the location bit being recording. This process may be referred to as “thermally-assisted magnetic recording” or “heat-assisted magnetic recording” (HAMR), and requires a magnetic recording head (as a component of a slider) that is capable of delivering heat to a magnetic disk in a highly precise fashion, for example by use of a laser diode unit (LDU).
In today's magnetic hard disk drive devices, each magnetic read or write head (“read head,” for short) is included as part of a head-gimbal assembly, which includes a suspension assembly that provides electrical connection to the read head. The suspension assembly typically includes a laminated flexure to carry electrical signals to and from the read head. The head-gimbal assembly is a component of a head-stack assembly that typically includes multiple head-gimbal assemblies, with each head gimbal assembly being attached at an end of an arm of an actuator.
Typically, as part of a finished suspension assembly, a read head is bonded to a portion of the laminated flexure by use of a substantially permanent adhesive. Consequently, if the read head is found to be defective after the read head has been attached to the head gimbal assembly, the entire suspension assembly must ordinarily be discarded, because the permanent bond cannot usually be broken without damaging the laminated flexure.
To prevent the need to discard a suspension assembly after a read head has been installed and subsequently found to be defective, a typical practice is to test a read head before permanently bonding the read head to the head gimbal assembly. If the read head is found to be defective by testing performed before the read head is bonded to the head gimbal assembly, the read head alone can be to discarded or repaired. Such functional testing (e.g., so-called “dynamic electrical testing” or “DET”) of a read head separate from the suspension assembly is more accurate if the testing conditions closely resemble actual conditions during operation of the read head. For example, the accuracy of the dynamic electrical testing may be improved by holding and electrically connecting the read head using a suspension assembly that is similar to the type of suspension assembly to which the read head will be bonded if its function is deemed acceptable.
Test assemblies that simulate a use condition during dynamic electrical testing have been proposed and used commercially, and must be continuously updated as the designs of read heads advance to include smaller, newer, or additional features. For example, as new versions of read heads are developed to include smaller or an increased number of contact pads, new designs of dynamic electrical testing devices must be developed to accommodate read heads (e.g., sliders) with the reduced-size features. As another example, as new sliders that include additional electrical functionality such as a laser diode unit are developed and commercialized, new systems for dynamic electrical testing must be developed to test these new read heads.